Recently, harmful substances, for example nitrogen oxide (NOx), discharged from a ship become more strictly prohibited (for reference, TierIII which is to be effective in 2016 is scheduled to regulate the discharge of nitrogen oxide below 3.4 g/KW (in case of less than rpm 130)), and thus various kinds of harmful substance reducing devices for ship utilizing a selective catalyst reduction (SCR) technique or the like are being widely developed and propagated.
For example, Korean Unexamined Patent Publication No. 10-2010-132310 (entitled “a SCR system for a ship using urea powder and nitrogen oxide reducing method”) (published on Dec. 17, 2010), Korean Unexamined Patent Publication No. 10-2013-127737 (entitled “an apparatus for preventing a SCR device from being clogged with waste heat of a ship”) (published on Nov. 25, 2013), Korean Unexamined Patent Publication No. 10-2014-46651 (entitled “a denitriding apparatus of a large engine for a ship”) (published on Apr. 21, 2014) or the like disclose more detailed configurations of existing harmful substance reducing devices for ship.
Meanwhile, as shown in FIG. 1, an existing harmful substance reducing device 10, for example a nitrogen oxide reducing device, is configured so that an exhaust gas flow line 12 drawn from an engine 11, a reducing agent storage tank 21 for storing a reducing agent (for example, urea) for reducing harmful substances, for example nitrogen oxide (NOx), a reducing agent injector 20 connected to the reducing agent storage tank 21 to inject the reducing agent (for example, urea) stored in the reducing agent storage tank 21 to the exhaust gas flow line 12, a compressed air supplier 22 for supplying a compressed air so that the reducing agent injector 20 may easily perform a series of reducing agent injecting functions, a controller 23 for controlling a compressed air supply valve 24 based on a measurement value output from sensors 19 to adjust an amount of reducing agent injected by the reducing agent injector 20, and a SCR reactor 13 connected to the engine 11 through the exhaust gas flow line 12 to allow an exhaust gas and a reducing agent to pass together so as to purify harmful substances (for example, nitrogen oxide (NOx)) contained in the exhaust gas are systematically combined.
At this time, the SCR reactor 13 allows the exhaust gas and the reducing agent to pass simultaneously so that the nitrogen oxide (NOx) reacts with the reducing agent, and is configured so that a SCR catalyst 18 for reducing the corresponding nitrogen oxide (NOx) into nitrogen and steam harmless to living things and a SCR chamber 17 accommodating the SCR catalyst 18 are combined.
Under such an existing system, if the output of the engine 11 increases, the scale of the harmful substance reducing device 10 inevitably increases proportionally. This is because, if the output of the engine 11 increases, an amount of exhaust gas generated from the corresponding engine 11 inevitably increases.
However, there are many limits in increasing the scale of the harmful substance reducing device 10 in proportion to the output of the engine 11. This is because, if the scale of the harmful substance reducing device 10 increases, various problems such as deteriorated space utilization of a ship, impossible overland transportation of the large harmful substance reducing device 10, impossible enlargement of various valves or the like occur.
If the enlargement of scale of the harmful substance reducing device 10 is restricted as above, a ship operator inevitably has great difficulty in purifying harmful substances generated from the engine 11 and should bear tangible or intangible damages resulting therefrom.